Transition metal catalysts have been employed to prepare polymers and copolymers of .alpha.-olefins. For the most part, the polymer properties have been controlled or varied by changes in the process conditions as disclosed by Hogan et al in U.S. Pat. No. 2,825,721; by Walker et al in U.S. Pat. No. 3,351,623; "The Polymerization of Olefins by Ziegler Catalysts", Bergy, M. N., et al, Advances in Catalysis, Vol. 19, and "Supported Chromium Catalysts for Ethylene Polymerization", Annual Symposium, Joint Meeting of the American Chemical Society and Chemical Society of Japan, Apr. 1-6, 1979.
It has now been discovered that the polymer properties can be varied by employing two different catalysts during polymerization of the .alpha.-olefin. Such polymerization process provides for one or more of the following:
(1) alteration of the physical properties of the polymer without changing process conditions; PA0 (2) change physical properties of the polymer without the use of hydrogen, PA0 (3) change polymer composition of copolymers by changing catalyst ratios rather than comonomer ratios and/or PA0 (4) increased catalyst efficiency. PA0 Mg:Ti is from about 0.1:1 to about 200:1 preferably from about 1:1 to about 100:1, and most preferably from about 10:1 to about 50:1. PA0 Al:Ti is from about 0.5:1 to about 200:1 preferably from about 1:1 to about 100:1, and most preferably from about 5:1 to about 50:1. PA0 xsX:Al is from about 0:1 to about 10:1 preferably from about 0.01:1 to about 1:1, and most preferably from about 0.1:1 to about 0.4:1. PA0 Ms:Cr is from 10:1 to about 1000:1, preferably from about 20:1 to about 500:1 and most preferably from about 50:1 to about 200:1. PA0 catalyst n productivity=Pn= ##EQU1## catalyst n yield=Yn=gms. catalyst n.times.unit time.times.Pn total yield=T=Yn+Ym PA0 catalyst n fractional % yield=Xn=Yn/T PA0 Xm=1-Xn